In der vorliegenden Arbeit wurden stickstoffhaltige Monomere ausgehend von aromatischen Aminen oder Lactamen durch Umsetzung mit Chlorsilanen synthetisiert. Die so erhaltenen Derivate wurden mit Hilfe spektroskopischer und thermischer Analysenmethoden umfassend charakterisiert. Auf Basis der stickstoffhaltigen Monomere wurden über unterschiedliche Synthesestrategien organisch-anorganische, nanostrukturierte Hybridmaterialien hergestellt. Durch die thermisch induzierte Zwillingspolymerisation der Monomere 2,2‘-Spirobi[3,4-dihydro-1H-1,3,2-benzodiazasilin] und 1,1’,4,4‘-Tetrahydro-2,2‘-spirobi[benzo[d][1,3,2]-oxazasilin] gelang es, Hybridmaterialien bestehend aus Polyanilin-Formaldehyd-Harzen und Polysilazanen bzw. Siliciumdioxid unter Variation der Reaktionstemperatur herzustellen. Die Untersuchung der entstandenen Materialien erfolgte mittels spektroskopischer Methoden. Die Lactam-Monomere wurden durch die Zugabe von Aminocarbonsäuren zu Polyamid 6/SiO2- bzw. Polysiloxan-Kompositen umgesetzt. Hier stand die Ermittlung der molekularen Struktur, wie auch die Bestimmung des thermischen Verhaltens und der Homogenität der Materialien im Vordergrund. Es konnte gezeigt werden, dass die Synthese der thermoplastischen Kompositmaterialien auch in vergrößertem Maßstab reproduzierbar ist und die Produkte zudem zu Folien extrudierbar sind. / In the present work nitrogen-containing monomers have been synthesized by reactions of silicon tetrachloride with amines or lactames and were characterized by different spectroscopic and thermal analysis methods. The twin monomers 2,2‘-spirobi[3,4-dihydro-1H-1,3,2-benzodiazasiline] and 1,1’,4,4‘-tetrahydro-2,2‘-spirobi[benzo[d][1,3,2]¬oxazasiline] can be converted to hybrid materials containing polyaniline-formaldehyde resins and polysilazane or SiO2 by thermal induced twin polymerization under variation of the reaction temperature. The obtained nano composites were investigated by spectroscopic methods and electron microscopy. The lactam containing monomers were polymerized to polyamide 6/SiO2-composites by addition of aminocarbonic acids and -caprolactam. The analysis of the molecular structure as well as the investigation of the thermal behavior and the homogeneity of materials was emphasized. It could be shown, that the synthesis can be performed reproducible. Furthermore, it is possible to extrude the thermoplastic composite materials to films.

Les liposomes sont des nanovecteurs polyvalents et prometteurs quant à leur utilisation dans plusieurs domaines. Il y a une décennie, un nouveau type de liposome constitué d’amphiphiles monoalkylés et de stérols est né fortuitement dans notre groupe. Ils sont nommés Stérosomes puisqu’ils contiennent une grande proportion de stérols, entre 50 et 70 mol %. Les objectifs de cette thèse sont de développer de nouvelles formulations de Stérosomes ayant des caractéristiques spécifiques et d’acquérir une compréhension plus profonde des règles physicochimiques qui dictent leur comportement de phase. Nous avons spécifiquement examiné le rôle de motifs moléculaires des stérols, de la charge interfaciale et de la capacité à former des liaisons H dans les interactions intermoléculaires menant à l’autoassemblage. Le comportement de phase a été caractérisé par calorimétrie différentielle à balayage (DSC), par spectroscopie infrarouge (IR) et par spectroscopie de résonance magnétique nucléaire du deutérium (²H NMR). Premièrement, nous avons établi certaines corrélations entre la structure des stérols, leur tendance à former des bicouches fluides en présence d'amphiphile monoalkylé et la perméabilité des grandes vésicules unilamellaires (LUV) formées. La nature des stérols module les propriétés de mélange avec de l’acide palmitique (PA). Les stérols portant une chaîne volumineuse en position C17 sont moins aptes à induire des bicouches fluides que ceux qui ont une chaîne plus simple, comme celle du cholestérol. Un grand ordre de la chaîne alkyle de PA est un effet commun à tous les stérols investigués. Il a été démontré que la perméabilité des LUV peut être contrôlée en utilisant des stérols différents. Cependant, ces stérols n’ont aucun impact significatif sur la sensibilité des Stérosomes au pH. Afin de créer des liposomes qui sont sensibles au pH et qui ont une charge positive à la surface, des Stérosomes composés de stéarylamine et de cholestérol (Chol) ont été conçus et caractérisés. Il a été conclu que l’état de protonation de l’amine, dans ce travail, ou du groupe carboxylique, dans un travail précédent, confère une sensibilité au pH et détermine la charge à la surface du liposome. Les premiers Stérosomes complètement neutres ont été fabriqués en utilisant un réseau de fortes liaisons H intermoléculaires. Le groupe sulfoxyde est capable de former de fortes liaisons H avec le cholestérol et les molécules d’eau. Une bicouche fluide métastable a été obtenue, à la température de la pièce, à partir d'un mélange équimolaire d’octadécyl méthyl sulfoxyde (OMSO) et de Chol. Ce comportement distinct a permis d’extruder le mélange pour former des LUV à la température de la pièce. Après 30 h, le temps de vie de la phase métastable, des Stérosomes stables et imperméables existaient toujours sous une forme solide. Un diagramme de température-composition a été proposé afin de résumer le comportement de phase des mélanges d’OMSO/Chol. Finalement, nous avons élaboré des Stérosomes furtifs en incorporant du polyéthylène glycol (PEG) avec une ancre de cholestérol (PEG-Chol) à l’interface de Stérosomes de PA/Chol. Jusqu’à 20 mol % de PEG-Chol peut être introduit sans perturber la structure de la bicouche. La présence du PEG-Chol n’a aucun impact significatif sur la perméabilité de la LUV. L'encapsulation active de la doxorubicine, un médicament contre le cancer, a été réalisée malgré la faible perméabilité de ces LUV et la présence du PEG à l’interface. L’inclusion de PEG a modifié considérablement les propriétés de l’interface et a diminué la libération induite par la variation de pH observée avec des LUV nues de PA/Chol. Cette formulation inédite est potentiellement utile pour l’administration intraveineuse de médicaments. / Liposomes are promising and versatile nanocarriers suitable for potential applications in many fields. A decade ago, a new type of liposomes formed from monoalkylated amphiphiles and sterols was born somehow fortuitously in our group. They are referred to as Sterosomes, because they contain a large proportion of sterols, between 50 and 70 mol %. The objectives of the present thesis are to develop novel Sterosome formulations with specific features, and to gain a deeper understanding of the physicochemical rules that dictate their phase behavior. We have specifically examined the role of the molecular features of sterols, of the interfacial charges and of the H-bond capacity in the intermolecular interactions leading to the self-assembly. The phase behavior was characterized by differential scanning calorimetry (DSC), infrared spectroscopy (IR), and nuclear magnetic resonance spectroscopy of deuterium (2H NMR). First, we have established some correlations between the structure of the sterols, the propensity to form fluid bilayers, and the permeability of the resulting large unilamellar vesicles (LUVs). The nature of the sterol modulates the properties of the mixture with palmitic acid (PA). Sterols bearing a bulky tail chain at C17 are less capable to induce fluid bilayers than those with a non-bulky tail chain, like that of cholesterol. A large ordering of the alkyl chain of PA is an effect exhibited by all of the investigated sterols. It is shown that the permeability of the LUVs can be controlled using different sterols. However, these sterols have no significant impact on the pH-sensitivity of Sterosomes. In order to create liposomes that are pH-sensitive and that have a positive surface charge, Sterosomes composed of stearylamine and cholesterol (Chol) were designed and characterized. It is concluded that the protonation/deprotonation state of the amine (in this work) and carboxylic acid (in previous work) groups confers the pH-sensitivity and determines the surface charge of the liposomes. The first completely neutral Sterosomes were crafted based on the creation of strong intermolecular hydrogen bond networks. The sulfoxide group was capable of forming strong hydrogen bonds with cholesterol and water molecules. In an equimolar octadecyl methyl sulfoxide (OMSO)/Chol mixture, a metastable fluid bilayer was obtained at room temperature. This distinct phase behavior allowed extruding the mixtures to form LUVs at room temperature. After 30 h, the life-time of the metastable phase, stable and impermeable Sterosomes still existed in the solid form. A temperature–composition diagram was proposed to summarize the phase behavior of OMSO/Chol mixtures. Finally, a further step was made to prepare “stealth” Sterosomes by incorporating polyethylene glycol (PEG) with a cholesterol anchor (PEG-Chol) at the interface of PA/Chol Sterosomes. Up to 20 mol % PEG-Chol can be introduced without disturbing the bilayer structure. The presence of PEG-Chol had no significant impact on the permeability of the resulting LUVs. Active-loading of an anti-cancer drug, doxorubicin, can be achieved despite the low permeability of these LUVs and the presence of the PEG at the interface. The inclusion of PEG modified considerably the interface properties and decreased significantly the pH-triggered release observed with naked PA/Chol LUVs. This novel formulation is potentially useful for the application of intravenous administration in the drug delivery field.

Le manque de thérapies innovantes en chimiothérapie humaine incite la communauté scientifique à s'intéresser à de nouvelles sources de composés bioactifs. Nous pouvons citer les métabolites secondaires de plantes, auxquels appartiennent les acides hydroxy pentacycliques triterpénoiques (AHPTs) et plus particulièrement les Acides Ursolique (AU), Oléanolique (AO) et Bétulinique (AB). Ces molécules font l'objet de nombreuses études qui tendent à démontrer leurs propriétés : anti-infectieuses, anticancéreuses, antiprolifératives, anti-inflammatoires, hépatoprotectrices. Le principal obstacle à leur utilisation à des fins thérapeutiques, reste l'insolubilité de ces AHPTs dans l'eau. L'objectif de ce travail a donc été d'augmenter leur hydrosolubilité. Dans un premier temps, en accord avec les recommandations et/ou normes existantes, nous avons démontré que le spectre d'activité antibactérienne de l'AU et de l'AO se limitait aux bactéries à Gram positif. Aucun AHPT n'a montré d'activité antifongique. Seul l'AB a montré une activité intéressante sur le Cytomégalovirus humain (hCMV) ; aucune activité antivirale n'ayant été retrouvée sur le Poliovirus. Enfin, l'AB, mais encore plus l'AU ont montré une activité anticancéreuse à l'encontre de cellules modèles de leucémie myéloïde chronique (LMC). Dans un deuxième temps, nous avons procédé à la fabrication et à l'étude de complexes entre les AHPTs et des cyclodextrines. Nous avons retenu la gamma-cyclodextrine (gamma-CD), qui présentait l'avantage de complexer les 3 AHPTs avec une constante de formation « moyenne » à « élevée ». Ces complexes AHPTs :gamma-CD ont été caractérisés en utilisant diverses techniques : chromatographiques, thermiques et spectrométriques. Nous avons conclu à l'obtention de complexes d'inclusion qui ont permis d'augmenter la solubilité des AHPTs. Dans une dernière partie, nous avons évalué les activités biologiques des complexes AHPTs : gamma-CD. Les résultats montrent que les complexes AU : gamma-CD et AO : gamma-CD restent actifs à l'encontre des bactéries à Gram positif (mais avec une efficacité plus faible) ; tandis que le complexe AB : gamma-CD se révèle être actif sur certaines bactéries. Le complexe AB : gamma-CD, et de façon surprenante le complexe AU : gamma-CD présentent une activité antivirale à l'encontre du hCMV. Enfin, la diminution de la cytotoxicité liée à la complexation des AHPTs accroit l'intérêt des molécules d'AU et d'AB sur les cellules de LMC / The lack of innovative therapies in human chemotherapy incites the scientific community to be interested in new sources of bioactive compounds. We can quote the secondary metabolites of plants, to which belong hydroxy pentacyclic triterpene acids (HPTAs) and more particularly Ursolic (UA), Oleanolic (OA) and Betulinic Acids(BA). These molecules are the subjetc of numerous studies which tend to demonstrate their properties: anti-infective, anticancer, antiproliferatives, anti-inflammatory and hepatoprotectrive. The main obstacle to their use in therapeutic purposes stays the insolubility of these AHPTs in the water. Thus the objective of this work was to increase their hydrosolubility. At first, in agreement with the recommendations and/or the existing standards, we demonstrated that the antibacterial spectra of UA and OA are limited to Gram-positive bacteria. No HPTA showed antifungal activity. Only the BA showed an interesting antiviral activity on human Cytomegalovirus (hCMV); no antiviral activity was on Poliovirus. Finally, the BA, but even more UA showed an anticancer activity against cellular model of chronic myeloid leukemia (CML). Secondly, we proceeded to the manufacturing and to the study of complexes between HPTAs and cyclodextrines. We retained gamma-cyclodextrine (gamma-CD), which presented the advantage to complex the 3 AHPTs with a constant of "average" to "raised". These HPTAs:gamma-CD complexes were characterized by using diverse techniques: chromatographic, thermal and spectrometric. We concluded in the obtaining of inclusion complexes which allowed increasing the solubility of the HPTAs. In a last part, we estimated the biological activities of the HPTAs:gamma-CD complexes. The results show that the UA:gamma-CD and OA:gamma-CD complexes remain active against Gram-positive bacteria (but with a weaker efficiency); whereas the BA:gamma-CD complex shows to be active on certain bacteria. The BA:gamma-CD complex, and in a surprising way the UA:gamma-CD complex presents an antiviral activity against the hCMV. Finally, the decrease of the cytotoxicity linked to the complexation of the HPTAs believes the interest of UA and of BA on CML cells

Polymeric materials have provided pathways to products that could not be manufactured otherwise. A new technology which merges the benefits of ceramics into these polymer products has created materials ideally suited to many different industries, like food packaging. Nano Scale Surface Systems, Inc. (NS3), a company which coats polymers with ceramic oxides like SiO2 through a process known as plasma enhanced chemical vapor deposition (PECVD), was interested in the feasibility of an in line measurement system for monitoring the deposited films on various polymer products. This project examined two different coated polymer products, polyethylene terephthalate (PET) beverage containers and biaxially oriented PET food packaging, commonly known as plastic wrap in an effort to determine the feasibility of an ellipsometry based measurement system for NS3’s purpose. Due to its extensive use in the semiconductor industry for monitoring films deposited on silicon, a measurement systems known as ellipsometry, adept at monitoring the thickness and refractive index of thin films deposited on various substrates, appeared to be an ideal system for the measurement of ceramic oxides deposited on various polymer substrates. This project set out to determine the feasibility of using an ellipsometry based measurement system to monitor ceramic films, specifically silicon oxides (SiOX), deposited on polymer products. A preliminary experiment determined linearly polarized light could induce a discernible change in polarized light traversing a coated beverage container relative to an uncoated container. However, the experiment lacked repeatability due to the measurement apparatus’ cheap setup, prompting the construction of a null (conventional) ellipsometer for further research. The curved surface of the beverage containers under study unnecessarily complicated the feasibility study so further research examined PECVD SiOX on biaxially oriented PET instead. Characterization of the PECVD SiOX-PET material was divided into three experiments, with the first two analyzing the SiOX film and PET substrate separately while the third analyzed them together. To assist with the characterization experiments, NS3 provided samples, both SiOX coated and uncoated, of various deposition thicknesses on silicon and biaxially oriented PET substrates. Null ellipsometry was used in conjunction with spectroscopic reflectometry to characterize the refractive index and thickness of the deposited films. The combined measurement systems found the refractive index of the deposited SiOX films to be between 1.461 and 1.465. The measured thicknesses resulting from the two measurement systems coincided well and were usually 10-20 nm thicker than the predicted thicknesses by the deposition processing parameters. Abeles’ method and monochromatic goniometry were attempted; however, the results had to be discarded due to irrecoverable errors discovered in the reflectance measurement. X-ray photoelectron spectroscopy (XPS) data provided by NS3 showed the deposited SiOX films to be homogeneous with stoichiometries between 2.15 and 2.23. Characterization of the uncoated biaxially oriented PET required numerous measurement systems. From spectroscopic transmission, trirefringent anisotropy was discovered, intertwined with thickness variations in the PET foil. Goniometry measurements displayed distinct interference curves resulting from rear interface reflections interfering with front interface reflections from the PET sample. Subsequent goniometric models produced multiple solutions due to an unknown optical phenomenon, probably scattering, which degraded the reflection measurements. However, a combined measurement technique utilizing goniometry and differential scanning calorimetry (DSC) determined the refractive indices of the polymer to be NX = 1.677, NY = 1.632 and NZ = 1.495 with a thickness of 11.343 μm and a volume fraction crystallinity of 35-41%. Utilizing the measured refractive indices, ellipsometric models produced only an adequate fit of the measured data due to the presence of depolarization caused by non-uniform PET thickness and scattering resulting from embedded microscopic crystallites. The majority of the error in the ellipsometric data was observed in the Δ measurement. XPS measurements of SiOX deposited on polypropylene (PP) provided by NS3 showed a heterogeneous interphase layer between the deposited oxide and the polymer substrate where the composition of the layer was continually changing. A similar region, which violates the homogenous assumption the ellipsometric model relied on, was anticipated for the SiOX-PET samples under investigation. The use of an effective medium approximation (EMA) to represent the interphase region was attempted, but failed to provide a decent model fit of the measured data. Depolarization and high optical anisotropy caused by the polymer substrate in combination with a heterogeneous interphase region and the effects of the deposited SiOX layer all interacted to prevent ellipsometric modelling of the null ellipsometry measurements conducted. Goniometry measurements were conducted on the thickest deposited SiOX film (approximately 100 nm) which allowed for the refractive index of the film to be approximated through Abeles’ method (n = 1.46); however the validity of this approximation was questionable given the presence of interference fringes resulting from interference between reflections at both the front and rear interfaces of the material. From the experiments conducted, it was concluded that null ellipsometry with conventional ellipsometric models could not adequately measure a SiOX film’s refractive index or thickness when deposited on biaxially oriented PET. The reasons for the failure were interactions between multiple sources of error which led to both measurement errors and inaccurate model assumptions. Use of generalized ellipsometry, possibly with spectroscopic ellipsometry, may overcome the failures of conventional ellipsometry when studying this complex optical material.

We are concerned with addressing the worst-case distributed source coding (DSC) problem in asymmetric and interactive communication scenarios and its application to data-gathering wireless sensor networks in enhancing their lifetime. First, we propose a unified canonical framework, obtained by considering different communication constraints and objectives, to address the variants of DSC problem. Second, as for the worst-case information-theoretic analysis, the notion of information entropy cannot be used, we propose information ambiguity, derive its various properties, and prove that it is a valid information measure. Third, for a few variants of our interest of DSC problem, we provide the communication protocols and prove their optimality. In a typical data-gathering sensor network, the base-station that wants to gather sensor data is often assumed to be much more resourceful with respect to energy, computation, and communication capabilities compared to sensor nodes. Therefore, we argue that in such networks, the base-station should bear the most of the burden of communication and computation in the network. Allowing the base-station and sensor nodes to interactively communicate with each other enables us to carry this out. Our definition of sensor network lifetime allows us to reduce the problem of maximizing the worst-case network lifetime to the problem of minimizing the number of bits communicated by the nodes in the worst-case, which is further reduced to the worst-case DSC problem in asymmetric and interactive communication scenarios, with the assumption that the base-station knows the support-set of sensor data. We demonstrate that the optimal solutions of the energy-oblivious DSC problem variants cannot be directly applied to the data-gathering sensor networks, as those may be inefficient in the energy-constrained sensor networks. We address a few energy-efficient variants of DSC problem and provide optimal communication protocols for the sensor networks, based on those variants. Finally, we combine distributed source coding with two other system level opportunities of channel coding and cooperative nature of the nodes to further enhance the lifetime of the sensor networks. We address various scenarios and demonstrate the dependence of the computational complexity of the network lifetime maximization problem on the complex interplay of above system-level opportunities.

High performance multifunctional epoxy resin systems are becoming increasingly important as matrix materials for the advanced composites used in aerospace, electronics, automotive and other industries. In a composite based on epoxy resin systems, a three-dimensional network of the matrix is formed around the reinforcing fibre as a result of the chemical reaction between the resin and the curing agent. This chemical process, known as curing, is an important event to he considered in the production of composite components made up of these resin systems. Two process parameters namely viscosity and chemical conversion are of paramount significance in the production of composite materials Curing studies of the resin systems based on these two parameters, would therefore assume great importance in deciding the performance reliability of the end product. The objectives of the present investigation are 1. to study the cure kinetics of three thermoset resin systems, viz., i) epoxy novolac (EPIT)/ diamino diphenyl methane{DDM), ii) trigylcidyl para- ammo phenol (TGPAP)/toluene diamine (TDA) and iii) tetraglycidyl diamino diphenyl methane (TGDDM)/pyridine diamine(PDA) using the cure kinetic models based on chemical conversion (α), Theological conversion (β) and viscosity. 2.to develop a correlation between a and viscosity (η) and modify an existing autocatalytic model based on α, to the viscosity domain and 3.to investigate the cure behaviour of these systems in terms of the TTT cure diagram and its associated models. EPN/DDM, TGPAP/PDA and TGDDM/PDA resin systems were chosen for the studies to represent a range of functionalities, The cure was monitored using differential scanning calorimetry (DSC), fourier transform infrared (FTIR) and dynamic mechanical analysis (DMA) techniques by following the changes in enthalpy, functional groups and rheology, respectively. The kinetic parameters namely, order of reaction and activation energy were estimated from dynamic DSC data using the methods of Freeman-Carroll and Ellerstein using nth rate expression. Barton, Kissinger and Osawa methods were employed to find out the activation energy from the peak/equal conversion at different heating rates. Isothermal DSC data were also analyzed using nth order model and it was observed that the data could be fitted satisfactorily only for higher temperatures The results obtained from the analysis of both dynamic and isothermal DSC data using nth order model clearly indicate that this model is inadequate for describing the cure behavior. The isothermal DSC data was analyzed by the autocatalytic models of Hone and Kamal Good correlation was observed with Hum and Kamal models up to 60-70%, 25% and 45% conversions for EPN/DDM, TGPAP/TDA and TCDDM/PDA systems respectively. However, the parameters m and n in Kamal model were found to be temperature dependent for EPN/DDM and TCPAP/TDA systems. The limited applicability of the autocatalytic models IK attributed to the counter-effect offered by the intra-molecular bonding taking place. The primary amine and epoxy groups conversions obtained from FTIR were analyzed using autocatalytic model and the kinetic parameters were calculated. The reactivity ratio of the primary amine and the secondary amine with epoxy was found to be dependent on temperature in agreement with the recent findings reported m the literature. The existing models that relate the cure kinetics and the rheological changes, are dual Arrhenius nth order model and autocatalytic model The nth order kinetic model was used to evaluate the kinetic parameters using the viscosity data at different cure temperatures under isothermal conditions As the storage modulus, G' is proportional to the chemical cross links and becomes significant only after the g<4 point, it was used to follow the changes in conversion known as rheoconversion after the gel point The rheoconversion was found by normalizing the G' data with G1^, the storage modulus of the fully cured resin It was used to study the cuie kinetics using an autocatalytic model The kinetic parameters such as rate constant, acceptation and retardation parameters were evaluated and that temperature dependence was established. While the existing models relate viscosity and conversion only up to gel point the new proposed model, termed VISCON model takes into account the changes up to vitrification. The relation so developed is used to modify the autocatalytic cure model based on chemical conversion. The parameters appearing in this model were evaluated using Levenberg-Marquardt error minimization algorithm. The kinetic parameters obtained are comparable with the values estimated using the DSC data. All the models cited above represent the microkinetic aspects. The models based on the information of TTT cure diagrams, however, represent the macrokinetic aspects of the cure, as they are based on the cure stages such as gelation and vitrification TTT diagram relates the cure characteristics like cure temperature, cure time, Ta and, indirectly, chemical conversion Hence the ultimate properties of the composite could he predicted and established with the help of the models based on TTT cure diagrams The changes in the storage modulus, G1 and loss modulus, G", were followed to identify the gel and vitrification points of the resin systems at different cure temperatures Gel point and vitrification point were used to generate gelation and vitrification hues in the construction of TTT cure diagrams for EPN/DDM, TGPAP/TDA and TGDDM/PDA resin systems Theoretical TTT diagrams were generated and IBO-T, contours were established using the TTT diagram-based models The cure schedule for the resin systems investigated could be determined from the TTT diagram and the respective rheological data.

The ability to tune the properties over a wide range of values by changing the additives, composition, etc., has made chalcogenide glassy semiconductors, most interesting from both fundamental physics as well as technology point of view. In particular, the occurrence of the two network topological thresholds namely the Rigidity Percolation Threshold (RPT) and the Chemical Threshold (CT) and their influence on various properties of chalcogenide glasses have been of immense interest during the last three decades. The Rigidity Percolation Threshold (also known as the Stiffness Threshold or Mechanical Threshold) corresponds to the composition at which the material transforms from a floppy polymeric glass to a rigid amorphous solid, whereas at Chemical Threshold the sample tends towards an ordered state. Though the rigidity percolation has been considered for long to occur at a critical threshold defined by the constraint’s theory, the recent theoretical and experimental investigations have found the RPT to occur over a range of compositions. In systems exhibiting an extended rigidity percolation, two distinct transitions namely from a floppy to an isostatically rigid phase and from an isostatically rigid to a stressed rigid phase are seen. In the category of chalcogenide glasses, tellurides have been found to exhibit interesting properties including the phenomenon of electrical switching which finds applications in Phase Change Memories (PCM). Studies on various thermal, electrical and photoelectrical properties of glassy tellurides help us in identifying suitable materials for different technological applications. This thesis deals with Differential Scanning Calorimetric (DSC) & Temperature Modulated Alternating Differential Scanning Calorimetric (ADSC) studies, electrical switching investigations, photoconductivity & photothermal measurements on certain metal doped telluride glasses. The composition dependence of properties such as glass transition & crystallization temperatures, switching voltage, thermal diffusivity, photosensitivity, etc., have been analyzed to obtain information about topological thresholds, thermally reversing window, etc. The first chapter of thesis provides an overview of properties of amorphous semiconductors, in particular chalcogenide glasses. The local & defect structure, the electronic band structure & electrical properties, electrical switching behavior, etc., are discussed in detail. The theoretical aspects related to the experiments undertaken in this thesis work have also been described. The instrumentation used for various experiments conducted to measure thermal, electrical, photoelectrical and photothermal properties have been discussed in chapter two. The chapter three deals with the photocurrent measurements on As40Te60-xInx (7.5 ≤ x ≤ 16.5) glasses. In these samples, it has been found that the photocurrent increases with illumination, which is understood on the basis of the large dielectric constant and also due to the presence of a large number of positively charged defect states. Further, the composition dependence of the conductivity activation energy and the photosensitivity exhibit a maximum at x = 12.5 (<r> = 2.65) and a minimum at x = 15.0 (<r> = 2.70) which has been identified to be the Rigidity Percolation Threshold (RPT) and the Chemical Threshold (CT) respectively. The results of electrical switching, DSC and Photothermal Deflection (PTD) studies on As20Te80-xGax (7.5 ≤ x ≤ 18.5) glasses, undertaken to elucidate the network topological thresholds, are described in chapter four. It has been found that all the As20Te80-xGax glasses studied exhibit memory type electrical switching. The switching voltage (VT) of these glasses increases monotonically with x, in the composition range 7.5 ≤ x ≤ 15.0. The increase in VT with gallium addition leads to a local maximum at x = 15.0 and VT decreases with x thereafter, reaching a distinct minimum at x = 17.5. Based on the variation with composition of the electrical switching voltages, the composition x = 15.0 and x = 17.5 have been identified to be the rigidity percolation and chemical thresholds of the As20Te80-xGax glassy system respectively. Further, the DSC studies indicate that As20Te80-xGax glasses exhibit a single glass transition (Tg) and two crystallization reactions (Tc1 & Tc2) upon heating. There is no appreciable change in Tg of As20Te80-xGax glasses with the addition of upto about10 atom% of Ga, whereas a continuous increase is seen in the crystallization temperature (Tc1). It is interesting to note that both Tg and Tc1 exhibit a maximum at x = 15.0 and a minimum at x = 17.5, the compositions identified to be the RPT and CT respectively by the switching experiments. The composition dependence of thermal diffusivity estimated from the PTD signal, indicate the occurrence of an extended stiffness transition in As20Te80-xGax glasses, with the compositions x = 9.0 and x = 15.0 being the onset and the completion of an extended rigidity percolation. A maximum and a minimum are seen in the thermal diffusivity respectively at these compositions. Further, a second maximum is seen in the thermal diffusivity of As20Te80-xGax glasses, the Chemical Threshold (CT) of the glassy system. The fifth chapter of the thesis describes the ADSC, electrical switching and photocurrent measurements on Ge15Te85-xInx (1 ≤ x ≤ 11) glasses. It is found there is not much change in the Tg of Ge15Te85-xInx glasses in the composition range 1 ≤ x ≤ 3. An increase is seen in Tg beyond x = 3, which continues until x = 11. Further, the composition dependence of non-reversing enthalpy shows the presence of a thermally reversing window in the compositions range x = 3 and x = 7. Electrical switching studies indicate that Ge15Te85-xInx glasses exhibit threshold type of switching at input currents below 2 mA. It is observed that switching voltages decrease initially with indium addition, exhibiting a minimum at x = 3, the onset of the extended rigidity percolation as revealed by ADSC. An increase is seen in VT above x = 3, which proceeds till x = 8, with a change in slope (lower to higher) seen around 7 atom% of indium which corresponds to the completion of the stiffness transition. The reversal in trend exhibited in the variation of VT at x = 8, leads to a well defined minimum around x = 9, the chemical threshold of the Ge15Te85-xInx glassy system. Photocurrent measurements indicate that there is no photodegradation in Ge15Te85-xInx glasses with x < 3, whereas samples with x ≥ 3 show photodegradation behavior. The composition dependent variation in the glass transition temperature has been attributed for this behavior. Further, the composition dependence of photo sensitivity has been found to show the signatures of the extended rigidity percolation and the chemical threshold in Ge15Te85-xInx glasses. The last chapter of thesis (chapter six) summarizes the results obtained and also the scope of future work to be undertaken.

Additives, incorporated in film coating formulations, and their process parameters are generally selected using a trial-and-error approach. However, coating problems and defects, especially those associated with aqueous coating systems, indicate the necessity of embracing a quality-by-design approach to identify the optimum coating parameters. In this study, the feasibility of using thermal and rheological measurements to help evaluate and design novel coating formulations has been investigated. Hydroxypropyl methylcellulose acetate succinate (HPMCAS), an enteric coating polymer, was used as the film forming polymer. Differential Scanning Calorimetry (DSC), Dynamic Mechanical Analysis (DMA), and Parallel Plate Shear Rheometery (PPSR) were used to evaluate the effect of different plasticisers on the performance of HPMCAS. The results illustrate that, for identical formulations, the DSC and DMA methods yielded up to 40% differences in glass transition temperature (Tg) values. Moreover, Tg measured using loss modulus signals were always 20-30 oC less than those measured using tan delta results in DMA testing. Absolute and relative Tg values can significantly vary depending on the geometry of the samples, clamp size, temperature ramping rate and the frequency of the oscillations. Complex viscosity data for different formulations demonstrated a variable shear thinning behaviour and a Tg independent ranking. It is, therefore, insufficient to rely purely on Tg values to determine the relative performance of additives. In addition, complex viscosity results, obtained using both the DMA and PPSR techniques at similar temperatures, are shown to be comparable. The results from both techniques were therefore used to produce continuous master curves for the HPMCAS formulations. Additionally, step strain tests showed that HPMCAS chains do not fully III disentangle after 105 seconds as predicted by the Maxwell model. Finally, in situ aqueous-based coating experiments proved that mixtures of triethyl acetyl citrate and acetylated monoglyceride (TEAC/AMG), even without cooling of the suspension, do not cause blocking of the spray nozzle whereas triethyl citrate (TEC) based formulae did. TEAC (alone or in a combination with AMG) exhibits superior wettability to HPMCAS than TEC/AMG formulations and can be used to enhance the efficiency and film quality of the dry coating process.

Non-metallic inclusions in steels are generally considered to be detrimental for mechanical properties. However, it has been recognized that certain inclusions, such as Ti-oxide and TiN, can serve as potent nucleation sites for the formation of intragranular ferrite (IGF) in low-alloy steels. The formation of IGF could improve the toughness of the coarse grained heat affected zone (CGHAZ) of weld metals. Thus, the present thesis mainly focuses on the effect of size of nucleation sites on the IGF formation. Quantitative studies on the composition, size distribution and nucleation probability for each size of the inclusions as well as the area fraction, starting temperature and morphology of an IGF have been carried out. In the present work, the Ti-oxide and TiN powders were mixed with metallic powders. The mixed powders were heated up to the liquid state and cooled with a slow cooling rate of 3.6 ºC/min. These as-cast steels with Ti-oxide and TiN additions were used to simulate the IGF formation in the CGHAZ of weld metals. Specifically, the inclusion and microstructure characteristics in as-cast steels have been investigated. The results show that the nucleant inclusion was identified as a TiOx+MnS phase in steels with Ti2O3 additions and as a TiN+Mn-Al-Si-Ti-O+MnS phase in steels with TiN additions. In addition, the TiOx and TiN phases are detected to be the effective nucleation sites for IGF formation. It is clearly shown that an increased inclusion size leads to an increased probability of IGF nucleation. This probability of IGF nucleation for each inclusion size of the TiOx+MnS inclusions is clearly higher than that of the complex TiN+Mn-Al-Si-Ti-O+MnS inclusions. In addition, the area fraction of IGF in the steels with Ti2O3 additions is larger than that of the steels with TiN additions. This result agrees with the predicted tendency of the probability of IGF nucleation for each inclusion size in the steels with Ti2O3 and TiN additions. In order to predict the effective inclusion size for IGF formation, the critical diameters of the TiO, TiN and VN inclusions, which acted as the nucleation sites of IGF formation, were also calculated based on the classical nucleation theory. The critical diameters of TiO, TiN and VN inclusions for IGF formation were found to be 0.192, 0.355 and 0.810 μm in the present steels. The calculation results were found to be in agreement with the experiment data of an effective inclusion size. Moreover, the effects of the S, Mn and C contents on the critical diameters of inclusions were also calculated. It was found that the critical diameter of the TiO, TiN and VN inclusions increases with an increased content of Mn or C. However, the S content doesn’t have a direct effect on the critical diameter of the inclusions for IGF formation. The probability of IGF nucleation for each inclusion size slightly decreases in the steel containing a higher S content. This fact is due to that an increased amount of MnS precipitation covers the nucleant inclusion surface. In the as-cast experiment, it was noted that an IGF can be formed in steels with Ti2O3 and TiN additions with a cooling rate of 3.6 ºC/min. In order to control the microstructure characteristics, such as the area fraction and the morphology of an IGF, and to investigate the starting temperature of IGF and grain boundary ferrite (GBF) formation, the dynamic transformation behavior of IGF and GBF was studied in-situ by a high temperature confocal laser scanning microscope (CLSM). Furthermore, the chemical compositions of the inclusions and the morphology of IGF after the in-situ observations were investigated by using scanning electron microscopy (SEM), electron backscatter diffraction (EBSD) and electron probe microanalysis (EPMA) which equipped wavelength dispersive spectrometer (WDS). The results show that the area fraction of IGF is larger in the steels with Ti2O3 additions compared to the steels with TiN additions, after the same thermal cycle has been imposed. This is due to that the TiOx phase provides more potent nucleation sites for IGF than the TiN phase does. Also, the area fraction of IGF in the steels is highest after at an intermediate cooling rate of 70 ºC/min, since the competing phase transformations are avoided. This fact has been detected by using a hybrid methodology in combination with CLSM and differential scanning calorimetry (DSC). In addition, it is noted that the morphology of an IGF is refined with an increased cooling rate. / <p>QC 20150325</p>

L'objectif de ces travaux a été de développer des vernis acrylate photo-polymérisables à 100% d'extrait sec, destinés à protéger des pièces thermoplastiques en polycarbonate contre les endommagements mécaniques, en particulier contre la rayure. Les relations entre la composition, la structure et les propriétés de ces revêtements ont été explorées. Pour ce faire ont été étudiées la morphologie, les propriétés thermomécaniques ainsi que la résistance à la rayure des matériaux. Cette dernière a été évaluée par des tests de micro-scratch. La cinétique de formation des réseaux polymères a elle aussi été étudiée, par photo-DSC. Tous les matériaux étudiés présentent, en analyse thermomécanique dynamique, un module élevé à l'état caoutchoutique ainsi qu'une large relaxation mécanique. Un vernis pétro-sourcé à 100% d'extrait sec, qualifié de standard, a servi de point de départ à ces travaux. Il a tout d'abord été comparé à un vernis commercial solvanté photo-polymérisable, spécialement conçu pour la protection de pièces thermoplastiques. Celui-ci s'est avéré être plus efficace en termes de résistance à la rayure. Dans un deuxième temps, a été étudiée l'influence sur les propriétés du vernis standard pétro-sourcé d'un monomère multicyclique entrant dans sa composition. La modification de son pourcentage n'a permis d'apporter aucun bénéfice en termes de résistance à la rayure. Des nanoparticules de silice, d'alumine ou de zircone, disponibles sous forme de dispersion dans un monomère acrylate, ont ensuite été incorporées dans le vernis standard pétro-sourcé. Une organisation particulière de la nano-silice et de la nano-alumine au sein des matériaux étudiés a pu être observée par microscopie électronique en transmission. Il a été constaté que le taux de charge doit être élevé pour observer une augmentation du module élastique et une amélioration de la résistance à la rayure du vernis (≥15% massique dans le cas de la nano-silice). Par ailleurs, l'ajout de 5% massique de nano-silice dans le vernis n'a conduit à aucune modification de sa cinétique de photo-polymérisation. Enfin, une partie des composés acrylate pétro-sourcés du vernis standard a été substituée par des acrylates bio-sourcés disponibles industriellement. La cinétique de photo-polymérisation des deux types de vernis est similaire. Les conclusions de la comparaison entre les vernis bio-sourcés et le vernis standard pétro-sourcé en termes de résistance à la rayure dépendent de l'épaisseur des revêtements étudiés. L'ajout d'un composé monoacrylate bio-sourcé à la formulation des vernis tend à améliorer la recouvrance élastique des revêtements de faible épaisseur. L'acrylate d'isobornyle est en particulier intéressant, car il a aussi tendance à retarder l'apparition des craquelures au cours de la rayure.